Investing should never be mandatory and should only be done with funds you can afford to lose. Especially for highly volatile and risky assets like cryptocurrencies. So I don't think it's a good idea to focus on a monthly plan if the amounts invested are substantial. People doing that should do it as a game of chance, without specific goals. If they win, they must be happy, but if they lose, it shouldn't affect them, they shouldn't have to care about it.
that only happened with investment that has significant risk though but with investment like buying gold or something of lesser risk no need to be cautious whether we gonna lose money after all we won't and even if it did its because the value of that commodity is getting down and we don't lost that much amount of money anyway.
just like bank deposits there's reason why they are so small in apy because the investment itself is quite secure, its just that people don't really like it because the interest only enough to cover for inflation.
but for investment like crypto that are quite volatile, and also quite risky but also have significant APY and easily make profit out of it it does make sense indeed to think about the strategy and only use money we can afford to lose.